Electrical control for sewing machines

ABSTRACT

This disclosure relates to a control system for a sewing machine wherein timed controlling of the operation of the sewing machine is accomplished through the use of a relatively simple switching circuit which is economically feasible.

United States Patent 1191 1111 3,793,566 Mailaender Feb. 19, 1974 [54] ELECTRICAL CONTROL FOR SEWING 3,644,793 2/1972 llk 317/141 S MACHINES 3,309,542 3/1967 B11161 517/154 x 2,643,305 6/1953 Mnnsson 200/611] 1 1 Inventor: Peter Maihender, Plattenhardt. 3,562,595 2/1971 Swanson 317/141 5 Germany 73 Assignee: Union Special Maschinenfabrik OTHER PUBLICATIONS GmbH Stuttgart Germany A Transistor Timer Radio and Television News 2 l No 2 1971 Garner, Oct. 1953, pp. 68, 69, 187.

[21] Appl. No.: 194,972

Primary ExaminerJames D. Trammell Assistant ExaminerHarry E. Moose, Jr. [30] Fm'e'gn Apphcanon Pnomy Data Attorney, Agent, or Firm Diller, Brown, Ramik &

Nov. 4, 1970 I Germany P 20 54 149.5 Wi ht [52] US. Cl...... 317/1485 R, 112/67, ZOO/61.58 R,

I 318/265, 318/446 57 ABSTRACT [51] Int. Cl. HOlh 47/32 [58] Field of Search 112/67, 219 A, 220; This disclosure relates to a control system for a sewing 317/D1G. 6, 154', 141 S; 318/11, 62, 265, machine wherein timed controlling of the operation of 446, 452; ZOO/61.58 R, 61.13, 16 D the sewing machine is accomplished through the use of a relatively simple switching circuit which is eco- [56] I References Cited nomically feasible.

' UNITED STATES PATENTS 15 Cl 2 D 3,665,872 5 1972 Hodgins 112 67 'awmg gums Pmminrfi w 3.793.566

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' czf' 54 HEW i T Zf I INVENTDR PETER MHlLAENDER ELECTRICAL CONTROL FOR SEWING MACHINES The invention relates to an electrical switching arrangement for sewing machines.

BACKGROUND OF THE INVENTION Electrical switching arrangements for sewing machines are well known. Both in the case of switching arrangements which are to be operated arbitrarily as well as in the case of such arrangements switched automatically by the machine during the operation thereof, mechancial switches are used which will switch the arrangement that is to be connected on or off directly or via switching relays. The disadvantage of such switches consists in the fact that they require relatively extended switching paths and also need long switching times. The time of switching, in the case of such switches, generally is fairly inexact.

For this reason special arrangements have already been made in the case of drives for sewing machines which will stop the machine in certain positions in order to determine the time of switching more precisely. For this purpose slip rings have been provided at the handwheel of the sewingmachine having a low r.p.m., in which contact elements are disposed, which make possible a relatively precise switching in regard to time via brushes. However, since these slip rings establish contact at every turn of the sewing machine, it will be necessary to provide additional switches that close the circuit to the slip rings either arbitrarily or controlled by the mechanism of the machine, whereupon the slip rings with the brushes will determine the exact time of the switching. The same controls also have been used with contactless synchronizers.

SUMMARY OF THE INVENTION necting the relay with a self-holding circuit and in that a second contact element and a second switching element are provided that constitute a switch for interruption of the self-holding circuit. As a result of this switching arrangement, it will be possible to switch the relay on at a certain point in the path of the operating cycle of a machine and to switch it off again at another point.

Between the second contact element and the holding circuit, there likewise is an amplifier circuit and the interruption of the holding circuit likewise is caused by charging a capacitor in the opposing direction through contact of the second contact element with the second switching element.

As a result of this switching arrangement, it will be possible during the operating cycle of a machine to allow both switches, constituted by the contact element, to each time carry out a switching impulse only once.

The switching arrangement is shown in detail in an embodiment in the case of a short seam machine having a two-speed motor.

-With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the'seva contact element, disposed in insulated relation to the housing of the machine, together with a switching element moved by a control arrangement, constitutes a switch, whereby the switching element, its bearing or the machine housing serve as electric conductors. The switch constituted by the contact element and a switching element is connected with a switching relay via an amplifying circuit. This circuit arrangement according to the present invention will permit the execution of a switching process in an economical manner at a certain point of the path in the course of the operation of one sewing process, for example in the course of operation of a short seam machine. In order to make the switching on of the switching relay determined by way of the path dependent on time, preferably a capacitor will precede the amplifying circuit, which capacitor upon contact of the switching element with the contact element will charge in an opposite direction and will impart thereby a switching impulse to the relay via the amplifier circuit.

In the further development of the switching arrangement, provision has been made to make the switching time of the switching relay, which is dependent on time, dependent on the path by way of the capacitor, by coneral views illustrated in the accompanying drawing.

IN THE DRAWING:

FIG. 1 is a schematic view of the driving and switching contact arrangement.

FIG. 2 is a wiring diagram.

In the case of a short seaming machine 1, shown in FIG. 1, the drive is accomplished by a two-speed motor 2 through a drive belt 3, which connects a pulley 4 on the motor shaft 5 with a pulley 6 on the drive shaft 7 of the sewing machine 1. The pulley 6 is freely rotatable with respect to the drive shaft 7 and is selectively coupled with the latter by means of a conventional coupling arrangement, such as a clutch.

In order to couple the pulley 6 to the drive shaft 7, there is a pedal 8 which through a connecting rod 9 and an elbow lever 11 shifts a bar 13 counter to the force of a spring 12, whereupon a lever 10 effects the coupling of the pulley 6 to the drive shaft 7 under the influence of a spring 14. Through engagement of the coupling, the sewing machine is driven and executes a controlled predetermined operating cycle by means of a known control arrangement not shown in detail. After completion of the operating cycle, the machine disengages automatically.

During the entire operating cycle of the sewing machine 1, the motor 2 runs'at its high speed and its speed is reduced just before the end of the operating cycle to its low speed in order to soften the disconnecting impact of the machine stopping in a certain position, for example with the needle raised.

The switching arrangement in the illustrated embodiment of the invention serves to switch the motor 2 by providing two contact elements 15 and 16. The contact element 15 together with a switching element 17 constitutes a switch S1 and contact element 16 together with a switching element 18 constitutes a switch element S2. The contact elements 15 and 16 are connected with the switch box 22 of the motor 2 by way of Wires 19, 21. The switching element 17 is located on a switch rod 23 which is shiftably mounted in the sew- 3. ing machine 1. The switching element 17 is in an electrically conductive connection with the machine housing via switching rod 23. The switching element 18 is seated on the bar '13, which also functions as a switch and, adjacent an insulating element'24. The bar or switch rod 13 is also connected electrically conductively with the housing'of the sewing machine through its bearings. The machine housing itself is connected with switch box 22 of the motor 2 by way of a wire 25.

With reference to the wiring diagram of FlG. 2, in the switch box 22 of motor 2, the switching arrangement for switching the motor 2 is fed by way of the feed line through a transformer Tr and a rectifier G1. The motor 2 receives its current directly from a power supply through a main switch, not shown, which has been provided in the customary manner for switching on and off. Upon switching the main switch on, the motor 2 is fed current through triacs Tyl and Ty2 and the terminals U1, V1, W1, and starts at a high speed. At thistime relay D1 remains unenergized and the control circuit is in the state shown in FIG. '2.

Energization of a relayDl will be prevented by. a i Zener diode G3. Transistor T2 is given acontrol voltage pulse before transistor T1, because the capacitor C3 mustcharge only before the control voltage is connected to the transistor T1, but there is insufficient time to raise thevoltage at the Zener diode G3 to such a point that current will flow through the Zenerdiode G3 to the transistor T2. Therefore, relay D1 is without current in the starting position shown, in which the switches 81 and S2are closed. I I By depression of pedal 8 and engagement of' the clutch, switch rod l3 also is shifte'd,-as a result of which i contact'element 16 moves from contact element 18 onto the insulating element 24. Asa result, switch S2 is opened, butbecause the current continues to flow through resistor R6, capacitor C5, diode G4 and transistor T3 toward the negative, 110 switching reaction takes place at transistor T3. After a predetermined operation of the sewing machine, switchSl, formed by contact element 15 and switch contact 17, is opened through. the automatic shifting of the switch rod 23 in a customary manner. Inthis case too nore'action takes place at transistor T1 because the current continues to flow toward the negative just as in the case of a closed switch 51 through resistor R1, capacitor C3, diode G2 and transistor T1..-

Opening of the switch S1 takes place, in the case of short seam sewing machine 1 being a buttonhole machine, when movement of the switch rod 23 is controlled by the movement of the clamp for the cloth being with the switch rod 23 being reciprocated in each operating cycle. In other words, the sewing machine 1 which has started operating at a high'speed continues to operate at this speed although in the meantime, both switches S1 and 82 have opened. I

After one side of a buttonhole has been completed in Zener diode G3, the transistor T2 toward thenega tive, as a result of which relay D1 closes contacts S3, S4 and S5 and opens contacts S6 and S7 This causes a shifting of motor 2 to its low r.p.m. speed by switchingthe triacs Ty3 and Ty4 to turned on positions and turning off the triacs Tyl and Ty2, and the motor now receives its current through terminals U2,V'2, W2.

I Since, as described previously, switch S2 opens and as a result of that current flows through transistor T3 transistor T4 is turned off and transistor T5 is turned on, so that the holding circuit for the relay D1 is closed via switch- S3. The'motor thus runs at'a low r.p;m. until switch S2 closes. Switch S2 will close whenever the clutch, controlled by a mechanical control arrangement in the machine,'disengages and the machine comes to a halt. Upon disengagement of the clutch, switchrod or bar 13 is positioned in the'starting' position, as'a result of which contactelement l6 againruns up oncontact element 18 and switch S2 is closed.

Upon the closing of switchZSZ, capacitor C5 recharges by the time determined by the resistor R6. During thepredetermined time, transistor. T3 turns off, as

a result of which transistor T4 is turned on and transis- "tor T5 is turned off.This results in the'deenergization of-the relay D1 and thus an opening of the holding cir cuitand aswitching over of the contact S3 to S7, as a result of which the motor 2 again is switched over to its high speed. i The capacitors C2 and C4, as well as resistors R2 and R7, have been provided to prevent faulty switchings in the'caseof chattering of. the contact elements, while capacitorfCl serves toequalizethe system. I

, As a resultot' theswitchi'ng arrangement according to the invention, one will achieve the effect that both switches willcause a switching impulse only during a closing each time by the recharging time of the capacitors, but that they will bring about any switchingaction subsequently either in their closed or in their opened state. ,A' new switching impulse is delivered only after opening and renewed closing of the switch. As a result of that, a sequence switching will become possible with simple means and'at low cost. At the same time, changes withinthe switching arrangement are possible without 9 impairing this effect. Thus, for example, contacts of relay 'lDl could be replaced by sem'i-' conductor constructional units. Also, the switch S2 could open and close several times between two switching impulses from the switch S1, for example, for-reathe case of abu'ttonhole machine and the machine has produced a bar tack and hasreturned on the second side of the buttonhole, the switching element 17 again runs onto the contact element 15. As a result of that, switch S1 is again closed. Now capacitor C3 reverses the charge via the resistors R3, R4, R2 and switch S1,

sons of construction of the control element, without causing a switching reaction on relay D1.

Although only a preferred embodiment of the invention and several apparent changes have been specifically disclosed, it will be readily apparent that "various other modifications may be made withoutdeparting from the spirit and scope of the invention, as defined by the appended claims. t "lclaim f v 1. In a sewing machine including-ian electrically conductive-sewing'machine housing, an electrical switchingarrangement comprising a switch including a fixed contact element ,and a switching element, means mounting said fixed contact element on said sewing machine housing in insulated relation thereto, a control member slidably movably mounted in said sewing machine housing in electrically contacting relation thereto, said switching element being mounted on said control member in electrically conducting relation thereto, said switching element being axially movable with said contact member between a contacting position and spaced relation relative to said fixed contact element in response to positioning of said control memher, and said sewing machine housing forming part of a conductor for said switching arrangement.

2. The switching arrangement of claim 1 together with a switching relay, and an amplifying circuit for energizing said switching relay, said amplifying circuit being controlled by said switch.

3. The switching arrangement of claim 2, wherein a capacitor precedes said amplifying circuit, said switch controlling the charging of said capacitor, and the. circuitry between said switching relay and said capacitor being such that said switching relay is energized during the charging of said capacitor.

4. The switching arrangement of claim 3 together with a self-holding circuit for said switching relay.

5. The switching arrangement of claim 4 together with a second switching arrangement for interrupting said holding circuit, said second switching arrangement including a second switch.

6. The switching arrangement of claim 5 wherein a second amplifying circuit is disposed between said second switch and said holding circuit.

7. The switching arrangement of claim 6 wherein said second switching arrangement includes a capacitor the charging of which is controlled by said second switch and wherein interruption of said holding occurs during charging of said second capacitor.

8. The switching arrangement of claim 5 wherein said second switching arrangement includes a capacitor the charging of which is controlled by said second switch and wherein interruption of said holding occurs during charging of said second capacitor.

9. The switching arrangementof claim 1 wherein said sewing machine includes an external control device, and said control member projects externally of said sewing machine housing and is associated with said control device for actuating the same.

10. The switching arrangement of claim 8 wherein said external control device is a mechanically actuated clutch.

11. The switching arrangement of claim 1 together with a foot pedal controlled actuator coupled to said control member for shifting the same.

12. A control circuit for a switching relay comprising a first switch means for both initiating and controlling current flow through said switching relay, a second switch means controlling actuation of said first switch means, and a control circuit for said second switch means including a capacitor, and third switch means for controlling the charging of said capacitor and thereby the operation of said second switch means and subsequently the operation of said first switch means to effect current flow through said switching relay and temporary current absorbing means between said first switch means and said switching relay.

13. A control circuit for a switching relay comprising a first switch means for both initiating and controlling current flow through said switching relay, a second switch means controlling actuation of said first switch means, and a control circuit for said second switch means including a capacitor, and third switch means for controlling the charging of said capacitor and thereby the operation of said second switch means and subsequently the operation of said first switch means to effect current flow through said switching relay, a selfholding circuit for said switching relay, and a switching arrangement-for interrupting said holding circuit, said switching arrangement including fourth switch means in said self-holding circuit, a second control circuit for said fourth switch means including a second capacitor, and fifth switch means for controlling the charging of said capacitor and thereby the operation of said fourth switch means. i

14. The control circuit of claim 13 wherein said second control circuit includes serially operative sixth and seventh switch means.

15. The control circuit of claim 14 wherein said third and fifth switch means are mechanical switch means and the others of said switch means are transistors.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent; 566 Dated February 19, 1974 Inventor It is certified that error appears in the above-identified patent and that said Letters Patentare hereby corrected as shown below:

Column 5,01aim 10, line 41 "8" should be --9-. 7' I Signed and sealed this 17th day of September 1974.

(SEALQ) Attest:

McCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner of- Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 793 566 Dat d February 19 1974 Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5,-claim 10; line 41 "8" should be 9-.

Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of- Patents FORM PC4050 v V USCOMM-DC 60376-P69 U.SI GOVERNMENT PRINTING OFFICE: I9, 0-366-33l, 

1. In a sewing machine including an electrically conductive sewing machine housing, an electrical switching arrangement comprising a switch including a fixed contact element and a switching element, means mounting said fixed contact element on said sewing machine housing in insulated relation thereto, a control member slidably movably mounted in said sewing machine housing in electrically contacting relation thereto, said switching element being mounted on said control member in electrically conducting relation thereto, said switching element being axially movable with said contact member between a contacting position and spaced relation relative to said fixed contact element in response to positioning of said control member, and said sewing machine housing forming part of a conductor for said switching arrangement.
 2. The switching arrangement of claim 1 together with a switching relay, and an amplifying circuit for energizing said switching relay, said amplifying circuit being controlled by said switch.
 3. The switching arrangement of claim 2, wherein a capacitor precedes said amplifying circuit, said switch controlling the charging of said capacitor, and the circuitry between said switching relay and said capacitor being such that said switching relay is energized during the charging of said capacitor.
 4. The switching arrangement of claim 3 together with a self-holding circuit for said switching relay.
 5. The switching arrangement of claim 4 together with a second switching arrangement for interrupting said holding circuit, said second switching arrangement including a second switch.
 6. The switching arrangement of claim 5 wherein a second amplifying circuit is disposed between said second switch and said holding circuit.
 7. The switching arrangement of claim 6 wherein said second switching arrangement includes a capacitor the charging of whiCh is controlled by said second switch and wherein interruption of said holding occurs during charging of said second capacitor.
 8. The switching arrangement of claim 5 wherein said second switching arrangement includes a capacitor the charging of which is controlled by said second switch and wherein interruption of said holding occurs during charging of said second capacitor.
 9. The switching arrangement of claim 1 wherein said sewing machine includes an external control device, and said control member projects externally of said sewing machine housing and is associated with said control device for actuating the same.
 10. The switching arrangement of claim 8 wherein said external control device is a mechanically actuated clutch.
 11. The switching arrangement of claim 1 together with a foot pedal controlled actuator coupled to said control member for shifting the same.
 12. A control circuit for a switching relay comprising a first switch means for both initiating and controlling current flow through said switching relay, a second switch means controlling actuation of said first switch means, and a control circuit for said second switch means including a capacitor, and third switch means for controlling the charging of said capacitor and thereby the operation of said second switch means and subsequently the operation of said first switch means to effect current flow through said switching relay and temporary current absorbing means between said first switch means and said switching relay.
 13. A control circuit for a switching relay comprising a first switch means for both initiating and controlling current flow through said switching relay, a second switch means controlling actuation of said first switch means, and a control circuit for said second switch means including a capacitor, and third switch means for controlling the charging of said capacitor and thereby the operation of said second switch means and subsequently the operation of said first switch means to effect current flow through said switching relay, a self-holding circuit for said switching relay, and a switching arrangement for interrupting said holding circuit, said switching arrangement including fourth switch means in said self-holding circuit, a second control circuit for said fourth switch means including a second capacitor, and fifth switch means for controlling the charging of said capacitor and thereby the operation of said fourth switch means.
 14. The control circuit of claim 13 wherein said second control circuit includes serially operative sixth and seventh switch means.
 15. The control circuit of claim 14 wherein said third and fifth switch means are mechanical switch means and the others of said switch means are transistors. 